Method of embossing plywood



Nov. 4, 1930. G. R. MEYERcoRD .Er AL 1,780,496

METHOD OF EMBVOSSING PLYWOOD Filed March l5, 1929 mw l/f f @A A fw? MPatented Nov. 4, 1930 UNITED STATES PATENT fori-ICE GEORGE R. MEYERCORD,OF CHICAGO, ILLINOIS, AND IB. NORRIS, F GRAND' RAPIDS, MICHIGAN,ASSIGNORS TO HASKELITE MANUFACTURING CORPORATION, A

CORPORATION OF NEW YORK METHOD OF EMBOSSING PLYWOOD Application ledHarch'lS, 1929. Serial No.` 347,436. A

and sharp and have the appearance of a Wood carving. The object of thepresentinvention is to make possible the commercial production oflembossed plywood panels, in which the embossing will be sharp and cleanand theouter layer of veneer be left without visible breaks or defectsresulting from the embossing process.

In order to secure al perfect product, the dies must ofcourse beaccurately made but, if a panel is compressed equally throughout itsarea, or if .the pressure and temperature factors are'not properlychosen, or if there is no provision for getting rid of the excessmoisture which the panel contains due to the boiling thereof to permitit to be molded, the resulting product will not be satisfactory. Thepanels to be embossed usually .consist of cores faced with veneers oftherarer woods. We have found that good results are not obltained unlessthe panel is highly compressed 1n areas where the embossing is heavy; areduction in thickness to one-half the initial thickness, or even less,being often necessary. However, if this same reduction in thickness iscarried to other parts of the panel where there is no embossing, forexample, the grain of the core will show through the veneer. Also, ifthe -dies are simply closed Von the work, and held closed, the surfaceof the panel will be blistered.

In one of its aspects our invention may be said to comprise a novelembossed plywood panel, together with a method for effective 1yproducing the same.

The' various features of novelty whereby our invention is characterizedwill hereinafter be pointed out lwith particularity in the' claims; but,for a full understanding of our. invention and of l its objects andadvantages, 'reference may be had to the follewing detailed descriptiontaken in connection with the accompanying drawing, wherein:

.LFigure 1 is an edge view of a fragment of "a plywood panel before theembossing operation; Fig. 2 is a section through a fragment of the samepanel, after the embossing' operation; Fier. 3 is a vertical sectionthrough a ypair of em ossing dies for transforming the panel of Figflinto the panel of Fig. 2; ndFig. 4 is a top plan view of the lowerAssuming that the plywood panel of Fig.

l is to be transformed into a panel having a novel embossed area 1surrounded by flat areas 2, 2 as indicated in Fig. 2, we have found thatthe material of the area l lis preferably compressed until the thicknessis reduced more than half whereas the flat areas 2 should be compressedonly slightly, in comparison. Where the flat areas are near the edges ofthe panel, the compression thereof need not be greater than telr percentwhereas, when they are located elsewhere, the reduction in thicknessshould be somewhat more, perhaps fifteen or twenty percent. l

The first requirement in the manufacture of the embossed panel is thatthe faces of the die blocks 3 and 4, including the dies 5 and 6, be soshaped that each part of the panel will be compressed to the desiredextent when thedies are closed on the panel under a predeterminedpressure. Therefore, if the die faces 5 and 6 f lt into each other whenthe dies are closed while empty, the surrounding llatfaces must be cutaway so that they will not touch.

Assuming that the dies have been properly made: the panel to be embossedis boiled until it has the requisite degree of pliability. Ordinarilycomparatively thin panels are boiled for about eight minutes. The panelis then placed between the 'dies and the dies are closed under a heavypressure. The pressure employed depends somewhat on the temperature, thelower the temperature the higher the pressure; We therefore prefer toheat the dies and have `found that good results are obtained by keepingthe dies at a temperature of about 300 F. The dies may be heated in anysuitable way as, for example,

by`means 'of electric .heating elements such as conventionally indicatedat 7 and 8 in Fig.

3. The pressure should be high at the beginning of the operation but,after the emboss- .ing has been fully developed and sharply defined, thepressure may be reduced while the panel is being thoroughly dried out,thereby to insure that the panel will lie fiat or have the desiredcurvature, when it is dry. Depending upon the nature of the panel andthe embossing to be applied, the high pressure may vary from threethousand pounds to six thousand pounds per square inch, while the lowpressure may in each case be about onethird as great as the highpressure.

If the dies are simply closed and left closed the surface of the panelwill become blistered. We have found that if the dies are opened fromtime to time during thefirst part of the embossing operation, the steamthat is generated will be caused to escape in such a manner that thesurface of the panel will remain unbleinished. Upon opening the dies,there is a sudden inrush of cool room air across the panel and auevolution of steam from the panel. Then, when the dies are quicklyclosed again, the steam and air are pushed out laterally. This briefopening of the dies should be brought about at intervals while there ismoisture to be eliminated. We have found in practice that if the diesare opened seven or eight times during the first five minutes of theembossing process, the dies may then be left closed, underheavypressure, for another/*period of say five minutes. By the end of thissecond period the embossing will have been clearly defined. Thereafterthe dies may be held closed until the panel has become dry; this thirdperiod usually lasting about fifteen minutes. Then, when the panel isremoved it will retain its shape indefinitely without warping.

The final product may be either flat, curved or molded into dish-shape,since the present invention relates to the impressing of embossing onthe panel rather than the shane of the panel itself. In any event, inorder to secure sharply defined embossing that will have the appearanceof band carving, heavily embossed areas must be highly compressed whilefiat or slightly rounded areas must be of a thickness more nearlyapproaching that of the original panel.

We claim:

1. The method of producing an embossed plywood panel which consists inboiling the panel, placing it between suitable complementary heateddies, alternately opening thefdies and closing them under a highpressure during a short period of time, and then holding the dies closedon the work until the latter has become dry.

2. The method of producing an embossed plywood panel which consists inboiling the panel, placing it between heated dies, closing the/dies uponthe panel under a high pressure, opening the dies at frequent intervalsduring the first part of the period during which they are closed underhigh pressure, and then holding the dies closed under a reduced pressureuntil the panel has dried.

3. The method of making an embossed plywood panel which consists inboiling a panel in -which the plies are united by waterproof glue,placing the panel between heatedcomplementary male and female dies,alternately opening the dies and closing them under high pressure for apredetermined period of time, then holding the dies closed under highpressure for a similar period of time, and keeping the'dies closed undera lower pressure for a longer period of time.

4. The method of producing an embossed plywood panel which consists inboiling a pannel in which the plies are united by waterproof glue,placing the panel between heated complementary dies, closing the dies onthe panel under high pressure for a period of about ten minutes, openingthe dies frequently during the first half of said period, and thereafterholding the dies closed under a lesser pressure until the plywood hasdried.

5. The method of producing an embossed plywood panel which consists inboiling a panel in which the plies are united by waterproof glue,placing the panel` between heated dies closingv the despn the panelunder high pressure for aperiod ofabout ten minutes, opening the diesfrequently during the first half of said period, and then holding thedies closed on the panel under a low pressure for a period of aboutfifteen minutes.

6. The method of making an embossed plywood panel which consists inboiling a panel in which the plies are united by waterproof glue,compressing the panel between complementary heated dies under a highpressure, opening the dies at intervals during the first part of theperiod of high pressure, and then holding the dies closed upon the panelunder a low pressure.

7. The method of producing an embossed plywood panel which consists inboiling a panel in which the plies are united by waterproof glue, anddeeply or heavily embossing areas surrounded by unembossed or onlyslightly embossed areas and at the same time compressing thefirst-mentioned areas to a greater extent than the latter areas.

In testimony whereof, we sign this specification. n

GEORGE R. MEYERCORD. CHARLES B. NORRIS.

